Prebiotic organic compounds in asteroid Bennu and Ryugu reflect divergent parent body histories
Angel Mojarro, José C. Aponte, Daniel P. Glavin, Jamie E. Elsila, Jason P. Dworkin, Harold C. Connolly
Geochimica et Cosmochimica Acta, In Press, Journal Pre-proof, Available online 4 October 2026
“The return of pristine samples from carbonaceous asteroids Ryugu by JAXA’s Hayabusa2 mission and Bennu by NASA’s OSIRIS-REx mission has enabled the direct comparative study of prebiotic organic compounds across the two primitive bodies. Using pyrolysis, thermochemolysis, and one-pot derivatization coupled to gas chromatography-triple quadrupole-mass spectrometry, we analyzed free volatile, insoluble, and soluble organic matter in a Ryugu aggregate and compared results to a Bennu aggregate and stones of interest. Pyrolysis of the Ryugu sample revealed polycyclic aromatic hydrocarbons, their alkylated homologues, and sulfur-, oxygen-, and nitrogen-bearing heterocyclic aromatic compounds consistent with aqueous alteration of the parent body. One-pot derivatization of the Ryugu aggregate yielded only tentative detections of β-alanine and 2,4-diaminopyrimidine. This is in contrast to the 14 proteinogenic α-amino acids and five canonical nucleobases previously detected across Bennu samples using the same technique. Thermochemolysis of the Ryugu sample revealed limited methylated derivatives while Bennu samples did not yield compounds above the procedural blank. The sparse thermochemolysis detections in samples from both asteroids are notable given that diverse methylated derivatives have been reported from the Orguiel (CI1) and Murchison (CM2) meteorites. We interpret these results as most likely originating from reagent-mineral interactions suppressing TMAH yields. Overall, contrasting organic inventories reflect divergent-parent body histories. Results from the Ryugu samples are consistent with a CI1-like classification, displaying increased alkylation of insoluble organic matter alongside depleted soluble organic matter abundances. In contrast, Bennu preserves heterogeneous organic signatures across stones recording multiple distinct alteration episodes. The presence of prebiotic molecules including amino acids and nucleobases across both asteroids further highlights the significance of carbonaceous bodies in contributing the chemical building blocks of life throughout the early Solar System.”
